Cutibacterium (formerly Propionibacterium) acnes clavicular infection

Cutibacterium (formerly Propionibacterium) acnes is a slow growing, gram-positive bacteria that is naturally found in higher concentrations as skin flora on the chest and back, as well as in other areas with greater numbers of hair follicles.^{25, 37} Most of the reported cases of C. acnes shoulder girdle infection follow arthroplasty surgery,^{18, 20, 26, 27, 32, 35} which then often requires debridement, administration of intravenous antibiotics, and surgical revision of the implanted device.^{12, 15, 21, 28-30} In a recent study, 56% of 193 shoulder revisions had a positive culture, 70% of which grew C. acnes.³⁰ Despite the relatively common presumed association of C. acnes humeral osteomyelitis with prosthetic infection, infection of the scapula or clavicle secondary to C. acnes is rare.^{4, 23, 36} Osteomyelitis of the clavicle involving any organism is also an uncommon event that can arise spontaneously via presumed hematogenous spread, or secondary to open fractures or internal fixation.^{6, 33} The most commonly found organism in clavicular osteomyelitis is Staphylococcus aureus.⁹ We here report two cases of clavicular infection secondary to C. acnes that were not associated with implants.